Introduction to medical accelerators Marco Silari CERN, Geneva, Switzerland 1 M. Silari - Medical particle accelerators African School of Physics 2010 ASP2010 - Stellenbosh (SA)
Introduction to medical accelerators
Marco SilariCERN, Geneva, Switzerland
1M. Silari - Medical particle accelerators
African School of Physics 2010
ASP2010 - Stellenbosh (SA)
1895
discovery of X rays
Wilhelm Conrad Röntgen
1897 “discovery” of the
electron
J.J. Thompson
The beginnings of modern physics and of medical physics
Courtesy Prof. Ugo Amaldi 2M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
(An accelerator for) Medical imaging
3M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
1930Ernest Lawrence invents the
cyclotron
M. S. Livingston and E. Lawrencewith the 25 inch cyclotron
Tools for (medical) physics: the cyclotron
4M. Silari - Medical particle accelerators Courtesy Prof. Ugo AmaldiASP2010 - Stellenbosh (SA)
James Chadwick(1891 – 1974)
1932
Discovery of the neutron
The beginnings of modern physics and of medical physics
5M. Silari - Medical particle accelerators
Cyclotron + neutrons = first attempt of radiation therapy with fast neutrons at LBL (R. Stone and J. Lawrence, 1938)
Courtesy Prof. Ugo AmaldiASP2010 - Stellenbosh (SA)
1939Invention of the klystron
William W. Hansen
1947 first linac for electrons
4.5 MeV and 3 GHz
Tools for (medical) physics: the electron linac
6
Sigmur Varian
Russell Varian
M. Silari - Medical particle accelerators Courtesy Prof. Ugo AmaldiASP2010 - Stellenbosh (SA)
1 GeV electron synchrotron
Frascati - INFN - 1959
1945: E. McMillan and V.J. Veksler
discover the principle of phase stability
6 GeV proton synchrotron
Bevatron - Berkeley - 1954
Tools for (medical) physics: the synchrotron
7M. Silari - Medical particle accelerators Courtesy Prof. Ugo AmaldiASP2010 - Stellenbosh (SA)
M. Silari - Medical particle accelerators 8
Accelerators operational in the worldThree main applications: 1) Scientific research2) Medical applications3) Industrial uses
CATEGORY OF ACCELERATORS NUMBER IN USE (*)
High-energy accelerators (E >1 GeV) ~ 120
Synchrotron radiation sources > 100
Medical radioisotope production ~ 200 ~ 1000
Accelerators for radiation therapy > 7500
Research accelerators including biomedical research ~ 1000
Industrial processing and research ~ 1500
Ion implanters, surface modification > 7000
TOTAL 17500 ~ 18000
10,000
Adapted from “Maciszewski, W. and Scharf, W., Particle accelerators for radiotherapy, Present status and future, Physica Medica XX, 137-145 (2004)”
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M. Silari - Medical particle accelerators 9
PSB
CPSvelocity
energy
c
Newton: 2
2
1mvE
SPS / LHC
Einstein:energy increasesnot velocity
2mcE }
Relativity
CERN accelerators
Medical cyclotrons and synchrotrons
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The betatron
• Magnetic field produced by pulsed coils• The magnetic flux inside the radius of the vacuum chamber changes with time• Increasing flux generates an azimuthal electric field which accelerates
electrons in the chamber
10M. Silari - Medical particle accelerators
)(2
1)( RBRB
= field at the orbit
)(RB = average flux density through the orbit
)(RB
Schematic diagram of betatron with air gap
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An old 45 MeV betatron for radiation therapy
11
The betatron
M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
MICROTRONE
Racetrack microtron
The microtronAn “electron cyclotron”• Uniform magnetic field• Fixed-frequency RF system• Well-separated orbits
12M. Silari - Medical particle accelerators
Bending radius
Revolution time
2
1
mc
eB
cp
eB
r
Be
mc
v
r
22
• Isocronism only if γ ≈ 1• If γ > 1, Δτ per turn = Δγ• To have isochronism it must be Δτ
per turn = hτRF
• Required energy gain per passageo for electrons ΔEe= 511 keVo for protons ΔEp= 938 MeV Magnet weight ≈ (energy)3
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Three classes of modern medical accelerators
Low-energy cyclotrons for production of radionuclides for medical diagnostics
Medium-energy cyclotrons and synchrotronsfor hadron therapy with protons (250 MeV)or light ion beams (400 MeV/u 12C-ions)
Electron linacs for conventional radiation therapy, including advanced modalities:
•Cyberknife•IntraOperative RT (IORT)•Intensity Modulated RT
13M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
e– + target X-rays
target
Medical linear electron accelerator
14M. Silari - Medical particle accelerators
Varian Clinac 1800 installed in the S. Anna Hospital in Como (Italy)
Multi-leaf collimator
3 GHz frequency
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Electron acceleration in a wave guide
15
Particles initially in cell 1 arrive in cell 2 to get further acceleratingkick. Frequency must match particles velocity and cell periodicity = ½ λ:
vf
M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Schematic drawing of a typical therapy head for a medical electron accelerator
16M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
M. Silari - Medical particle accelerators 17
No flattening filter Uses circular cones of diameter 0.5 to 6 cm Non-Isocentric Average dose delivered per session is 12.5 Gy 6 sessions/day Dose rate @ 80 cm = 400 cGy/min
http://www.accuray.com/Products/Cyberknife/index.aspx
CyberKnife (CK) Robotic Surgery System
6 MV Linac mounted on a robotic arm
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An example of intensity modulated treatment planning with photons. Through the addition of 9 fields it is possible to construct a highly conformal dose distribution with good dose sparing in the region of the brain stem (courtesy of T. Lomax, PSI).
E. Pedroni, Europhysics News (2000) Vol. 31 No. 6
Intensity Modulated Radiation Therapy (IMRT)
Yet X-rays have a comparatively poor energy deposition as compared to protons and carbon ions
18M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
The cyclotron
19M. Silari - Medical particle accelerators
Scanditronix MC40
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Motion of a particle in a dipole magnetic field (the field is in/out of the plane of this slide)
Bρ = 33.356·p [kG·m] = 3.3356·p [T·m] (if p is in GeV/c)
20
,2
mvF where ρ = radius of curvature of the path
2mvevBF
e
p
e
mvB
(p = momentum = mv)
M. Silari - Medical particle accelerators
Bρ is called “magnetic rigidity” of the particle and is an index of how difficult is to bend the motion of a charged particle by a magnetic field
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The cyclotron
21M. Silari - Medical particle accelerators
F = q(E = v x B)
mv2 / ρ = qvB
Rev. frequency f = qB/2πm
Rev. period τ = 1/f is independent of v
Resonant acceleration with fRF = h∙f
Isochronism
Maximum energy/nucleon:
T/A = k (Bρ)2 (Z/A)2
with k = e2 / 2mp
K = k (Bρ)2 is called “bending limit”K = 48 (Bρ)2 (MeV)if B is in teslas and m in metres
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22
The classical (non relativistic) cyclotron
Magnetic fields of uniform-field cyclotron:(top) Sectional view of cyclotron magnetic poles showing shims for optimizing field distribution.(left) Radial variation of vertical field magnitude and field index.
M. Silari - Medical particle accelerators
• Weak focusing• Decrease of rev. frequency f with r• Loss of isochronism Two solutions to achieve higher energies:
- synchrocyclotron- AVF cyclotron
BF
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23
The AVF (isochronous) cyclotron
M. Silari - Medical particle accelerators
AVF = azimuthally varying field
B(r,θ) = <B(r)> + Mod(r, θ)
o RF constanto <B> rises with radius r to
compensate for the relativistic increase of the particle mass
f = q<B>/2πmγ
Vertical focusing achieved by the azimuthal variation of B
A further component of the axial focusing force is obtained by giving the sectors a spiral shape
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“hadrons” are
made of quarks
carbon ion =
6 protons + 6 neutrons
atom
Proton or
neutron
quark “u” or “d”
electron “e”
Hadrontherapy: n, p and C-ion beams
24M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Proton radiation therapy
25M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Clinical results
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52 -83 %31 – 75 %5 year survivalSoft-tissue carcinoma
77 %61 %24-28 %local control
rateSalivary gland
tumours
100 %23 %5 year
survivalLiver tumours
7.8 months6.5 monthsav. survival
timePancreatic carcinoma
63 %21 %local control
rateParanasal sinuses
tumours
96 % (*)95 %local control
rateChoroid melanoma
16 months12 monthsav. survival
timeGlioblastoma
63 %40 -50 %5 year survivalNasopharynx
carcinoma
89 %88 %33 %local control
rateChondrosarcoma
70 %65 %30 – 50 %local control
rateChordoma
Results carbonGSI
Results carbonHIMAC-NIRS
Results photonsEnd pointIndication
Table by G. Kraft 2007
Results of C ions
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Cyclotrons and synchrotrons for proton therapy
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Accel-Varian
Hitachi
Loma Linda(built by FNAL)
IBA
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Proton versus carbon-ion synchrotrons
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G. Coutrakon, Accelerators for Heavy-charged-particle Radiation Therapy, Technology in Cancer Research & Treatment, Volume 6, Number 4 Supplement, August 2007
Hitachi proton synchrotron Siemens ion synchrotron
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Hadron-therapy in the world
29M. Silari - Medical particle accelerators
C • Carbon ion radiotherapy facilities
C • Carbon ion radiotherapy facilities (in planning stage of under construction)
• Proton radiotherapy facilities
Courtesy NIRS
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Loma Linda University Medical Center (LLUMC)
30M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Loma Linda University Medical Center (LLUMC)
31M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
M. Silari - Medical particle accelerators 32
A PT facility is not just the accelerator…
A gantry is a massive structure that allows directing the beam to the tumour from any direction. It carries• the final section of the beam line • the beam spreading ‘nozzle’• the proton ‘snout’ which carries
the aperture and range compensator
What it looks like to the patient: gantry room at the Midwest Proton Radiotherapy Institute (MPRI)(modified IBA gantry)
Adapted from B. Gottschalk
The IBA proton gantry
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33M. Silari - Medical particle accelerators
The LLUMC proton synchrotron
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We have already seen the motion of a particle in a dipole magnetic field…
Bρ = 33.356·p [kG·m] = 3.3356·p [T·m] (if p is in GeV/c)
34
,2
mvF where ρ = radius of curvature of the path
2mvevBF
e
p
e
mvB
(p = momentum = mv)
M. Silari - Medical particle accelerators
Bρ is called “magnetic rigidity” of the particle and is an index of how difficult is to bend the motion of a charged particle by a magnetic field
ASP2010 - Stellenbosh (SA)
Trajectory of a particle in a bending magnet
Two particles in a dipole field, with same momentum but different initial angles
Unfortunately an accelerator contains more than one particle!
Number of circulating particles in a synchrotron is typically in the order of 1010 - 1012 and more
35M. Silari - Medical particle accelerators
Trajectory of particles in a dipole field
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Photo: courtesy ANL
Quadrupoles as thin lenses
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Light rays passing through a series of focusing and defocusing lenses
The lenses, which are concave in one plane, are convex in the other
In both cases the concave lenses will have little effect as the light passesvery close to their centre, and the net result is that the light rays arefocused in both planes
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The mechanical equivalent
The gutter below illustrates how the particles in a synchrotron behave due to the quadrupolar fields.
Whenever a particle beam diverges too far away from the central orbit the quadrupoles focus them back towards the central orbit.
37M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Photo courtesy Fermilab Visual Media Services
G. Kraft, Proc. of CAARI 2008, AIP, p. 429
Hadron-therapy in Europe
38M. Silari - Medical particle accelerators
О in operation
◊ in constructionΔ planned
Yellow = p onlyOrange = p and C
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National Centre for Oncological hadrontherapy (CNAO) in Pavia
Courtesy S. Rossi, CNAO
39M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
National Centre for Oncological hadrontherapy (CNAO) in Pavia
40M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
Dipole magnetsQuadrupole magnets RF cavity
Ion sources LEBT components
41
The CNAO synchrotron
M. Silari - Medical particle accelerators
Injector linac
Courtesy S. Rossi, CNAO
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Heavy Ion Therapy Unit at the University of Heidelberg clinics
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The HIT heavy ion gantry, weight about 600 tons
Courtesy HIT
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North European Radio-oncological Centre in Kiev
43M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
PROSCAN at PSI, Switzerland
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ACCEL
SC cyclotron
250 MeV protons
PROSCAN
TERA
Courtesy PSI and U. Amaldi , TERA
J.M. Schippers et al., NIM BB 261 (2007) 773–776
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Hadron-therapy in Japan
45M. Silari - Medical particle accelerators
C: carbon ions, p: protons• in operation• under construction
Courtesy NIRS
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HIMAC in Chiba
46M. Silari - Medical particle accelerators
K. Noda et al., Recent progress on HIMAC for carbon therapy, Proc. of PAC09
The gantry “only” weighs 350 t
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Some new concepts
47M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
TERA Cyclinac=cyclotron+linac for Image Guided Hadron-therapy
48M. Silari - Medical particle accelerators
The energy is adjusted in 2 ms in the full range by changing the power pulses sent to the 16-22 accelerating modules
The charge in the next spot is adjusted every 2 ms with the computer controlled source
chopped beam at 200-400 Hz
linacmodules of LIGHT
computer controlled source
fast-cycling beam for tumour multi-painting
RF generatorsgantry
IBA structure
(synchro)cyclotron
beams used for other medical purposes
Courtesy U. Amaldi, TERA
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IDRA = Institute for Diagnostics and Radiotherapy
49M. Silari - Medical particle accelerators
30 MeV cyclotron by IBA
R A D I O P H A R M A C Y
P R O T O N T H E R A P Y
≤230 MeV
30 MeV
70 MeV
Linac for Image Guided
Hadron Therapy = LIGHT
15 m
Solid Statemodulator +klystron
A.D.A.M. SA, Application of Detectors and Accelerators to Medicine, a CERN spin-off company will build LIGHT, and has an agreement with IBA for the delivery of the rest and the overall control
A proton cyclinac Courtesy U. Amaldi, TERA
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The 250-300 MeV SC cyclotron designed by LNS, Italy
50M. Silari - Medical particle accelerators
The superconducting cyclotron
accelerates particles with Q/A = ½
12C6+ 6p+ + 6n
H2+ 2p+ + 1e-
Output energies:
protons 250 MeV
carbon ions 3000-3600 MeV
p
C
p / C
foil
4.9 mdeflector
SCENT = Superconducting Cyclotron for Exotic Nuclei and Therapy
L. Calabretta et al, NIM A 562 (2006) 1009 -1012
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CABOTO = Carbon Booster for Therapy in Oncology
51M. Silari - Medical particle accelerators
CABOTO -S (3 GHz)CABOTO -C (6 GHz)CABOTO -X (9 GHz)
design projects
Collaboration: EPFL and CERN - CLIC
SC EBIS source byDREBIT – Dresden300 Hz – 108 C/pulse
SC Synchrocyclotron230 MeV/uH2
+ and C+6
@ 300 Hz
400 MV – 3-9 GHz linac≤ 1.5 μs pulses
5 m
≤ 18 m
230 MeV/u 430 MeV/u
Two sources:
12C6+ H2+
Courtesy U. Amaldi, TERA
TERA Foundation, Italy
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IBA 400 MeV/u carbon-ion cyclotron
52M. Silari - Medical particle accelerators
Courtesy Y. Jongen, IBA
• Maximum energy: 400 MeV/u, adjustable externally by ESS
• Superconducting magnet. Hill field 4.5 T
• Cooling by helium loop, with 4 external recondensers
“Archade” (at Ganil in Caen, France) is based on the new IBA 400 MeV/u superconducting cyclotron
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Still River Systems
53M. Silari - Medical particle accelerators
Courtesy L. Bouchet, Still River Systems
Synchrocyclotron
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Still River Systems
54M. Silari - Medical particle accelerators
Synchrocyclotron @ 10 TeslaProton energy: 250 MeV Ion source tested up to 1,000 nACooling is through cryo-compressors (NO liquid Helium)Low maintenance requirements – quarterly onlyTime structure: similar to linear accelerator with gating and scanning capabilities
Weight ≈ 20 tons
Courtesy L. Bouchet, Still River Systems
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Multi-room versus single-room facilities
55M. Silari - Medical particle accelerators
29 m (87ft)
14 m (41 ft)
13
m (
39
ft)
Other Proton Systems
28
m (
84
ft)
812 m2
182 m2
2,240 m2
714 m2
Courtesy L. Bouchet, Still River Systems
Advantages of single-room facility: Modularity Reliability / back-up PT treatment available at more hospitals (Hopefully) cost
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Some textbooks
56M. Silari - Medical particle accelerators ASP2010 - Stellenbosh (SA)
C.K. Karzmark, Advances in linear accelerator design for radiotherapy, Medical Physics 11, 105- 128 (1984)
S. Humphries, Principles of charged particle acceleration, John Wiley and Sons
H. Wiedemann, Particle accelerator physics, Springer- Werlag
S. Baird, Accelerators for pedestrians, CERN AB-note-2007-014
PTCOG: Particle Therapy Co-Operative Grouphttp://ptcog.web.psi.ch/